共查询到20条相似文献，搜索用时 15 毫秒
1.
Amir H. Hosseini Clayton V. Deutsch Kevin W. Biggar Carl A. Mendoza 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(5):735-749
The spatial distribution of residual light non-aqueous phase liquid (LNAPL) is an important factor in reactive solute transport
modeling studies. There is great uncertainty associated with both the areal limits of LNAPL source zones and smaller scale
variability within the areal limits. A statistical approach is proposed to construct a probabilistic model for the spatial
distribution of residual NAPL and it is applied to a site characterized by ultra-violet-induced-cone-penetration testing (CPT–UVIF).
The uncertainty in areal limits is explicitly addressed by a novel distance function (DF) approach. In modeling the small-scale
variability within the areal limits, the CPT–UVIF data are used as primary source of information, while soil texture and distance
to water table are treated as secondary data. Two widely used geostatistical techniques are applied for the data integration,
namely sequential indicator simulation with locally varying means (SIS–LVM) and Bayesian updating (BU). A close match between
the calibrated uncertainty band (UB) and the target probabilities shows the performance of the proposed DF technique in characterization
of uncertainty in the areal limits. A cross-validation study also shows that the integration of the secondary data sources
substantially improves the prediction of contaminated and uncontaminated locations and that the SIS–LVM algorithm gives a
more accurate prediction of residual NAPL contamination. The proposed DF approach is useful in modeling the areal limits of
the non-stationary continuous or categorical random variables, and in providing a prior probability map for source zone sizes
to be used in Monte Carlo simulations of contaminant transport or Monte Carlo type inverse modeling studies. 相似文献
2.
Contamination of Drinking Water with Coliform Organisms by the Larves of Gnats in the Water Treatment Plant E. coli and coliform organisms are used to judge the microbial quality of drinking water. The presence of these organisms in water indicates that there is a risk for faecal oral transmitted pathogen organisms. E. coli shows the faecal contamination of men and warm blooded animals (mammalian and birds), coliform organisms may be excreted as well from cold blooded animals. The cold blooded animals normally don’t excrete pathogen organisms relevant for human beings. So coliform organisms don’t have such a high relevance for drinking water microbiology. In this paper an incident is presented with a contamination of drinking water with coliform organisms in the treatment plant by the larves of gnats. The larves of the gnats crawl into the treatment chamber via entrance for ventilation. The larves were kept back on the surface of the filters but they contaminated the water with coliform organisms. 相似文献
3.
Yoon-Seok Timothy Hong Byeong-Cheon Paik 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(5):695-707
Developing a mathematical model for predicting fecal coliform bacteria concentration is very important because it can provide a basis for water quality management decisions that can minimize microbial pollution risk to the public. This paper introduces a hybrid modeling methodology which is a combined use of a neural network-based pattern analysis and an evolutionary process model induction system. The neural network-based pattern analysis technique is applied to extract knowledge on inter-relationships between fecal coliform concentrations and other measurable variables in a sewer system. Based on the result of neural network-based pattern analysis, an evolutionary process model induction system is used to derive mathematical inference models that can predict fecal coliform bacteria concentration from easily measurable variables instead of directly measuring fecal coliform bacteria concentration in a sewer system. The neural network-based pattern analysis extracts that temperature and ammonia concentration are the most important driving forces leading to an increase in fecal coliform bacteria concentration in the sewer system at Paraparaumu City, New Zealand. Fecal coliform bacteria concentration is also positively correlated with dissolved phosphorus and inversely with flow rate. The multivariate inference models that are able to predict fecal coliform bacteria concentration are successfully derived as functions of flow rate, temperature, ammonia, and dissolved phosphorus in the form of understandable mathematical formulae using the evolutionary process model induction system, even if a priori mathematical knowledge of the dynamic nature of fecal coliform bacteria is poor. The multivariate inference models evolved by the evolutionary process model induction system produce a slightly better performance than the multi-layer perceptron neural network model. 相似文献
4.
David Huard Alain Mailhot Sophie Duchesne 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(3):337-347
Intensity–duration–frequency (IDF) curves are used extensively in engineering to assess the return periods of rainfall events
and often steer decisions in urban water structures such as sewers, pipes and retention basins. In the province of Québec,
precipitation time series are often short, leading to a considerable uncertainty on the parameters of the probabilistic distributions
describing rainfall intensity. In this paper, we apply Bayesian analysis to the estimation of IDF curves. The results show
the extent of uncertainties in IDF curves and the ensuing risk of their misinterpretation. This uncertainty is even more problematic
when IDF curves are used to estimate the return period of a given event. Indeed, standard methods provide overly large return
period estimates, leading to a false sense of security. Comparison of the Bayesian and classical approaches is made using
different prior assumptions for the return period and different estimation methods. A new prior distribution is also proposed
based on subjective appraisal by witnesses of the extreme character of the event. 相似文献
5.
6.
Allan D. Woodbury Tadeusz J. Ulrych 《Stochastic Environmental Research and Risk Assessment (SERRA)》1998,12(5):317-358
The similarity between maximum entropy (MaxEnt) and minimum relative entropy (MRE) allows recent advances in probabilistic
inversion to obviate some of the shortcomings in the former method. The purpose of this paper is to review and extend the
theory and practice of minimum relative entropy. In this regard, we illustrate important philosophies on inversion and the
similarly and differences between maximum entropy, minimum relative entropy, classical smallest model (SVD) and Bayesian solutions
for inverse problems. MaxEnt is applicable when we are determining a function that can be regarded as a probability distribution.
The approach can be extended to the case of the general linear problem and is interpreted as the model which fits all the
constraints and is the one model which has the greatest multiplicity or “spreadout” that can be realized in the greatest number
of ways. The MRE solution to the inverse problem differs from the maximum entropy viewpoint as noted above. The relative entropy
formulation provides the advantage of allowing for non-positive models, a prior bias in the estimated pdf and `hard' bounds
if desired. We outline how MRE can be used as a measure of resolution in linear inversion and show that MRE provides us with
a method to explore the limits of model space. The Bayesian methodology readily lends itself to the problem of updating prior
probabilities based on uncertain field measurements, and whose truth follows from the theorems of total and compound probabilities.
In the Bayesian approach information is complete and Bayes' theorem gives a unique posterior pdf. In comparing the results
of the classical, MaxEnt, MRE and Bayesian approaches we notice that the approaches produce different results. In␣comparing
MaxEnt with MRE for Jayne's die problem we see excellent comparisons between the results. We compare MaxEnt, smallest model
and MRE approaches for the density distribution of an equivalent spherically-symmetric earth and for the contaminant plume-source
problem. Theoretical comparisons between MRE and Bayesian solutions for the case of the linear model and Gaussian priors may
show different results. The Bayesian expected-value solution approaches that of MRE and that of the smallest model as the
prior distribution becomes uniform, but the Bayesian maximum aposteriori (MAP) solution may not exist for an underdetermined
case with a uniform prior. 相似文献
7.
The similarity between maximum entropy (MaxEnt) and minimum relative entropy (MRE) allows recent advances in probabilistic
inversion to obviate some of the shortcomings in the former method. The purpose of this paper is to review and extend the
theory and practice of minimum relative entropy. In this regard, we illustrate important philosophies on inversion and the
similarly and differences between maximum entropy, minimum relative entropy, classical smallest model (SVD) and Bayesian solutions
for inverse problems. MaxEnt is applicable when we are determining a function that can be regarded as a probability distribution.
The approach can be extended to the case of the general linear problem and is interpreted as the model which fits all the
constraints and is the one model which has the greatest multiplicity or “spreadout” that can be realized in the greatest number
of ways. The MRE solution to the inverse problem differs from the maximum entropy viewpoint as noted above. The relative entropy
formulation provides the advantage of allowing for non-positive models, a prior bias in the estimated pdf and `hard' bounds
if desired. We outline how MRE can be used as a measure of resolution in linear inversion and show that MRE provides us with
a method to explore the limits of model space. The Bayesian methodology readily lends itself to the problem of updating prior
probabilities based on uncertain field measurements, and whose truth follows from the theorems of total and compound probabilities.
In the Bayesian approach information is complete and Bayes' theorem gives a unique posterior pdf. In comparing the results
of the classical, MaxEnt, MRE and Bayesian approaches we notice that the approaches produce different results. In␣comparing
MaxEnt with MRE for Jayne's die problem we see excellent comparisons between the results. We compare MaxEnt, smallest model
and MRE approaches for the density distribution of an equivalent spherically-symmetric earth and for the contaminant plume-source
problem. Theoretical comparisons between MRE and Bayesian solutions for the case of the linear model and Gaussian priors may
show different results. The Bayesian expected-value solution approaches that of MRE and that of the smallest model as the
prior distribution becomes uniform, but the Bayesian maximum aposteriori (MAP) solution may not exist for an underdetermined
case with a uniform prior. 相似文献
8.
将府河从都江堰宝瓶口段至望江公园段分设9个监测点,在秋冬、春夏两季分别取水,首次建立由细菌总数、总大肠菌群数及粪大肠菌群数三个微生物学指标组成的体系,对府河两季水质进行对比监测分析,以综合评价水质、分析季节影响因素并反映出污染物来源.以都江堰宝瓶口大肠杆菌耐药率作为背景值,对整个河段的9个采样点分离纯化鉴定得到102株大肠杆菌,用K-B法进行对比药敏试验.结果表明,府河从都江堰段起,穿过成都市区后,至望江公园段细菌总数、大肠菌群数及粪大肠菌群数虽有波动,但细菌总数总体呈增加趋势,春夏季府河营养富集,水质有所降低.府河中大肠杆菌耐药性较小,β-内酰胺类耐药率在0.96％～33.33％之间,氨基糖苷类1.39％～7.84％,氟喹诺酮类11.43％～11.76％,磺胺类复方新诺明为52.78％,其中β-内酰胺类耐药性、氟喹诺酮类耐药性与源头水质有关,其余与医疗机构排放的废水及生活污水有关,此研究为控制成都府河水体中的污染防控提供了理论依据. 相似文献
9.
E. Aghaarabi F. Aminravan R. Sadiq M. Hoorfar M. J. Rodriguez H. Najjaran 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(3):655-679
This paper presents the use of two multi-criteria decision-making (MCDM) frameworks based on hierarchical fuzzy inference engines for the purpose of assessing drinking water quality in distribution networks. Incommensurable and uncertain water quality parameters (WQPs) at various sampling locations of the water distribution network (WDN) are monitored. Two classes of WQPs including microbial and physicochemical parameters are considered. Partial, incomplete and subjective information on WQPs introduce uncertainty to the water quality assessment process. Likewise, conflicting WQPs result in a partially reliable assessment of the quality associated with drinking water. The proposed methodology is based on two hierarchical inference engines tuned using historical data on WQPs in the WDN and expert knowledge. Each inference engine acts as a decision-making agent specialized in assessing one aspect of quality associated with drinking water. The MCDM frameworks were developed to assess the microbial and physicochemical aspects of water quality assessment. The MCDM frameworks are based on either fuzzy evidential or fuzzy rule-based inference. Both frameworks can interpret and communicate the relative quality associated with drinking water, while the second is superior in capturing the nonlinear relationships between the WQPs and estimated water quality. More comprehensive rules will have to be generated prior to reliable water quality assessment in real-case situations. The examples presented here serve to demonstrate the proposed frameworks. Both frameworks were tested through historical data available for a WDN, and a comparison was made based on their performance in assessing levels of water quality at various sampling locations of the network. 相似文献
10.
Bonkosky M Hernández-Delgado EA Sandoz B Robledo IE Norat-Ramírez J Mattei H 《Marine pollution bulletin》2009,58(1):45-54
Human fecal contamination of coral reefs is a major cause of concern. Conventional methods used to monitor microbial water quality cannot be used to discriminate between different fecal pollution sources. Fecal coliforms, enterococci, and human-specific Bacteroides (HF183, HF134), general Bacteroides-Prevotella (GB32), and Clostridium coccoides group (CP) 16S rDNA PCR assays were used to test for the presence of non-point source fecal contamination across the southwestern Puerto Rico shelf. Inshore waters were highly turbid, consistently receiving fecal pollution from variable sources, and showing the highest frequency of positive molecular marker signals. Signals were also detected at offshore waters in compliance with existing microbiological quality regulations. Phylogenetic analysis showed that most isolates were of human fecal origin. The geographic extent of non-point source fecal pollution was large and impacted extensive coral reef systems. This could have deleterious long-term impacts on public health, local fisheries and in tourism potential if not adequately addressed. 相似文献
11.
We evaluated microbiological water quality in the Pettaquamscutt River (Rhode Island, USA), an estuarine river. Fecal coliform (FC) and enterococci (FE) bacteria, presence of Bifidobacterium adolescentis DNA (indicating human fecal contamination), and optical brightener (OB) fluorescence (associated with laundry detergents) were determined for 14 stations from May to September 2010. Six stations had high counts of FE and FC, and the presence of B. adolescentis DNA and high OB fluorescence indicated human fecal contamination - four had septic systems as likely sources of contamination; the others were in sewered areas. The ability of FC and FE to indicate human fecal contamination was assessed against a positive B. adolescentis test. FC and FE had false positive rates of 25% and 17%, respectively, and false negatives of 44% for FC and 63% for FE. Inclusion of molecular and chemical indicators should improve tracking of human fecal contamination sources in the river. 相似文献
12.
It is important that indicators of fecal pollution are reliable. Coliform bacteria are a commonly used indicator of fecal pollution. As other investigators have reported elsewhere, we observed a seasonal pattern of coliform bacteria detections in domestic wells in New Jersey. Examination of a statewide database of 10 years of water quality data from 93,447 samples, from 78,207 wells, generated during real estate transactions, revealed that coliform bacteria were detected in a higher proportion of wells during warm weather months. Further examination of the seasonal pattern of other data, including well water pH, precipitation, ground and surface water temperatures, surface water coliform bacteria concentrations, and vegetation, resulted in the hypothesis that these bacteria may be derived from nonfecal (or environmentally adapted) as well as fecal sources. We provide evidence that the coliform seasonality may be the result of seasonal changes in groundwater extraction volumes (and to a lesser extent precipitation), and temperature‐driven changes in the concentration of surface or near‐surface coliform sources. Nonfecal coliform sources may not indicate the presence of fecal wastes and hence the potential presence of pathogens, or do so in an inconsistent fashion. Additional research is needed to identify the sources of the coliforms detected in groundwater. 相似文献
13.
Seung-Jae Lee Elizabeth A. Wentz Patricia Gober 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(2):283-295
Managing environmental and social systems in the face of uncertainty requires the best possible forecasts of future conditions.
We use space–time variability in historical data and projections of future population density to improve forecasting of residential
water demand in the City of Phoenix, Arizona. Our future water estimates are derived using the first and second order statistical
moments between a dependent variable, water use, and an independent variable, population density. The independent variable
is projected at future points, and remains uncertain. We use adjusted statistical moments that cover projection errors in
the independent variable, and propose a methodology to generate information-rich future estimates. These updated estimates
are processed in Bayesian Maximum Entropy (BME), which produces maps of estimated water use to the year 2030. Integrating
the uncertain estimates into the space–time forecasting process improves forecasting accuracy up to 43.9% over other space–time
mapping methods that do not assimilate the uncertain estimates. Further validation studies reveal that BME is more accurate
than co-kriging that integrates the error-free independent variable, but shows similar accuracy to kriging with measurement
error that processes the uncertain estimates. Our proposed forecasting method benefits from the uncertain estimates of the
future, provides up-to-date forecasts of water use, and can be adapted to other socio-economic and environmental applications. 相似文献
14.
Marta Rodrigues Anabela Oliveira Martha Guerreiro André Bustorff Fortunato José Menaia Luís Mesquita David Alexandra Cravo 《Ocean Dynamics》2011,61(6):841-856
This study aims at understanding the fecal contamination behavior in a small coastal stream (Aljezur, Portugal), which has
significant economic and ecological values. Like in most small coastal systems, circulation and water renewal in the Aljezur
stream exhibit a strong variability due to their dependence on tides, waves, intermittent river flows, and a highly variable
morphology. Hence, the problem was approached through a combination of field surveys and the development and application of
a hard-coupled three-dimensional hydrodynamic and fecal contamination model. Salinity and temperature results have shown that
mixing and transport in the stream are very sensitive to the river flow and wind forcing. The model is able to represent the
main patterns and trends observed in Escherichia coli and fecal enterococcus concentrations along the stream, for different environmental and contamination conditions, suggesting
die-off rates on the order of 0.50–0.55 day−1. Die-off rate and the representation of the sediment-associated processes were identified as the major remaining sources
of uncertainty in the model. Results show that, owing to the processes that occur along the stream, fecal bacteria reach the
beaches water in numbers that comply with the European Bathing Waters Directive, even during the summer periods when the upstream
concentrations are larger. In particular, results suggest a direct relation between the tidal propagation upstream and the
reduction of the fecal bacteria concentrations along the stream that can be relevant for the development of a strategy for
the management of the system’s water safety. 相似文献
15.
The bacteriological indices of water quality, including coliforms, sulfite-reducing clostridia, total microbial count, coliphages, and fecal streptococci were analyzed. A model describing fluctuations in microorganism population in the aquatic environment is proposed. A stochastic differential equation was obtained and used to derive a lognormal distribution of organism population. The model was applied to describe time series of bacteriological indices of the Moskva River Water Source. Satisfactory agreement was obtained between theoretical distributions and empirical data in a wide range of index values embracing one to three orders of variations in microorganism population. A forecast procedure was developed and applied to calculate the exceedance probabilities of different levels of bacterial pollution of the water source. Time periods with higher bacterial pollution were identified. 相似文献
16.
Ortega Ernesto Braunstein Alfredo Lage-Castellanos Alejandro 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(3):493-511
Stochastic Environmental Research and Risk Assessment - We present a Bayesian approach for the Contamination Source Detection problem in water distribution networks. Assuming that contamination is... 相似文献
17.
by Michiel Pronk Nico Goldscheider Jakob Zopfi and François Zwahlen 《Ground water》2009,47(3):361-369
Recharge and contamination of karst aquifers often occur via the unsaturated zone, but the functioning of this zone has not yet been fully understood. Therefore, irrigation and tracer experiments, along with monitoring of rainfall events, were used to examine water percolation and the transport of solutes, particles, and fecal bacteria between the land surface and a water outlet into a shallow cave. Monitored parameters included discharge, electrical conductivity, temperature, organic carbon, turbidity, particle-size distribution (PSD), fecal indicator bacteria, chloride, bromide, and uranine. Percolation following rainfall or irrigation can be subdivided into a lag phase (no response at the outlet), a piston-flow phase (release of epikarst storage water by pressure transfer), and a mixed-flow phase (increasing contribution of freshly infiltrated water), starting between 20 min and a few hours after the start of recharge event. Concerning particle and bacteria transport, results demonstrate that (1) a first turbidity signal occurs during increasing discharge due to remobilization of particles from fractures (pulse-through turbidity); (2) a second turbidity signal is caused by direct particle transfer from the soil (flow-through turbidity), often accompanied by high levels of fecal indicator bacteria, up to 17,000 Escherichia coli /100 mL; and (3) PSD allows differentiation between the two types of turbidity. A relative increase of fine particles (0.9 to 1.5 μm) coincides with microbial contamination. These findings help quantify water storage and percolation in the epikarst and better understand contaminant transport and attenuation. The use of PSD as "early-warning parameter" for microbial contamination in karst water is confirmed. 相似文献
18.
We assessed short-term ecological and potential human health effects of wastewater treatment plant (WTP) effluent by measuring δ15N‰ and microbial concentrations in oysters and suspended particulate matter (SPM). We also tested male-specific bacteriophage (MSB) as an alternative to fecal coliforms, to assess potential influence of wastewater contamination on shellfish. WTP effluent did not affect oyster growth or survival, but SPM and oysters acquired wastewater-specific δ15N‰. δ15N values were depleted near the WTP, typical of low-level processed wastewater. Fecal coliform and MSB concentrations were higher in samples taken closest to the WTP, and MSB values were significantly correlated with δ15N‰ in oyster tissues. Overall, oysters demonstrated relatively rapid integration and accumulation of wastewater-specific δ15N‰ and indicator microorganisms compared to water samples. These data suggest oysters were superior sentinels compared to water, and MSB was a more reliable indicator of wastewater influence on shellfish than fecal coliforms. 相似文献
19.
Public health authorities generally recommend annual water-quality monitoring of rural water wells and shock chlorination if coliforms are detected. It is implicitly assumed that shock chlorination is effective in ridding most wells of bacteriological pathogens for months to years. Neither annual monitoring nor shock chlorination was effective in addressing coliform contamination of selected water wells in a small town developed on an alluvial aquifer where septic system effluents are impacting well water quality. Considerable temporal variation in total and fecal coliforms was observed in water wells monitored for a six-month period. Individual wells intermittently met and exceeded the drinking water criteria, indicating annual sampling was insufficient. Shock chlorination of three contaminated wells and their associated distribution systems proved ineffective because colonies apparently originated from outside the wells and reappeared over relatively short time periods (ranging from less than one week up to 21 weeks). The relatively fast and similar rate of recovery of total heterotrophic bacteria suggested they are related to biofilm formation in the wells and not to ground water contamination. 相似文献
20.
Five years of monthly data of indicator bacteria from 1998 to 2002 were evaluated to find out the changes in water quality during the rehabilitation of the Golden Horn, an estuary severely polluted from industrial and domestic discharges since the 1950s. Surface fecal coliform was above 10(6) CFU/100 ml at the inner part in 1998. Following the achievement of healthy water circulation and control of most surface discharges, fecal coliform and fecal streptococci counts decreased below 10(3) CFU/100 ml in the summer of 2002. However, the decrease was interrupted by sudden shifts in rainy periods. Runoff, enhanced by domestic inputs during rainfall, has become the main factor influencing water quality in the estuary today. Increasing values of fecal coliform were observed during periods of low salinity, pH, dissolved oxygen and high ortho-phosphate, whilst decreasing values were detected during high salinity, pH and dissolved oxygen and low ortho-phosphate periods. Striking changes were observed within five years, promising that even an anoxic water body can turn into a recreational area with appropriate treatment. 相似文献